The process of lumber stacking involves a stacker, a conveyor conveying lumber pieces, e.g., 8' to 12' long and 2".times.4" in cross section, to the stacker where the pieces are accumulated into layers, e.g., twelve 2".times.4" pieces making up a layer and stacking the layers one on top of the other but separated by stickers. The stickers are laid perpendicular to the length of the lumber pieces at, e.g., 2' intervals. The stickers separate the layers by about 1"-2" to allow air flow above and below the layers (and between the spaced apart stickers).
Speed is of the essence and whereas the lumber can be accumulated and stacked in layers very rapidly, the bottleneck has long been considered the placement of the stickers between the layers. One form of the lumber stacking apparatus used for placing the stickers between layers provides a sticker holding pan attached alongside the forks of the stacker. As the forks receive a layer of lumber pieces and with the stickers residing in the sticker pan below the top side of the fork whereat the lumber is received, the layer is carried to the stack and as the layer is deposited on the stack, so too are the stickers deposited under the layer. This process is disclosed in U.S. Pat. Nos. 4,253,787 and 4,324,521, the disclosures of which are incorporated herein in their entirety.
As disclosed in these patents, the process of sticker placement involves cycling the forks back and forth between lumber receiving and stack depositing positions. Just prior to the step of lumber receiving and with the forks positioned below the next layer of lumber pieces, the fork movement is paused to allow time for the stickers to be picked off a sticker conveyor by a transfer mechanism and deposited into the pan. It is an object of the present invention to avoid the necessity of pausing the fork movement and with such avoidance, to shorten the stacking time and increase the rate of lumber stacking.